1. Field of the Invention
The present invention relates to an internal combustion engine ignition device, for example, mounted on a vehicle, and particularly to an internal combustion engine ignition device that generates an ignition high voltage across the secondary coil of an ignition coil, by flowing and interrupting an electric current for the primary coil of the ignition coil by use of a switching element.
2. Description of the Related Art
In a conventional internal combustion engine ignition device, an ion signal and an ignition signal are multiplexed and outputted on a coil-driver input signal line, and in the case where the ion signal is outputted, masking is performed so that the switching element does not turn on (for example, refer to Japanese Patent Laid-Open Pub. No. 2004-156608, Pages 17 and 18, FIGS. 49 and 50).
In the conventional internal combustion engine ignition device, there has been a problem that, in the case where, when the ion signal and the ignition signal are outputted at the coil-driver input signal line, the inside of the engine compartment becomes high-temperature, thereby causing pre-ignition, or a smolder occurs around the ignition plug, thereby producing soot between the electrodes, causing a leakage electric current to flow, and causing a pseudo ion current to flow constantly, it is required that the dynamic range of the input voltage be set wide in order to detect the ion current even at the timing when the ignition signal is supplied; as a result, the circuit scale of the ECU (Electronic Control Unit) becomes large, thereby causing the cost hike.
Moreover, there has been a problem that, in the case where a certain factor such as interruption of the primary-coil current causes a difference between the ground potential for the ECU and the ground potential for the coil driver, the ion signal cannot accurately be transferred to the ECU.